John 6

Then they said to him, “What must we do, to be doing the works of God?”  
Jesus answered them, “This is the work of God, that you believe in Him whom He has sent.”

But I said to you that you have seen me and yet you do not believe. 
All that the Father gives me will come to me, and whoever comes to me I will never cast out.  
For I have come down from heaven, not to do my own will but the will of Him who sent me.
And this is the will of Him who sent me, that I should lose nothing of all that He has given me, but raise it up on the last day.
 
For this is the will of my Father, that everyone who looks on the Son and believes in Him should have eternal life, and I will raise him up on the last day.

No one can come to me unless the Father who sent me draws him. And I will raise him up on the last day.
Everyone who has heard and learned from the Father comes to me—Truly, truly, I say to you, whoever believes has eternal life.

It is the Spirit who gives life; the flesh is no help at all. 
This is why I told you that no one can come to me unless it is granted him by the Father. 
Did I not choose you, the Twelve?